Knot brush with polymer-encapsulated knots

ABSTRACT

A rotary brush having a hub having a central bore, a plurality of wire knots extending radially outward from the hub and spaced apart from each other around an outer circumference of the hub, a thermosetting polymer encapsulating each wire knot, and substantially polymer-free spaces located between each adjacent pair of wire knots.

FIELD

The present disclosure relates to a rotary wire knot brush having wire knots that are encapsulated with a thermosetting polymer while the spaces between adjacent knots remain substantially free of polymer, and a method for encapsulating the individual knots of a rotary wire knot brush in a thermosetting polymer, while leaving the spaces between adjacent knots substantially free of polymer.

BACKGROUND

In the discussion of the background that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art.

In wire knot brushes known in the art, for example as disclosed in U.S. Pat. No. 4,504,997, bundles of wire strands may be looped through openings in a disk and twisted to form knots. Side plates located on either side of the disk are used to hold the knots in place, leaving an annular working portion of knots extending radially outward from the disk. During use, such a brush is mounted on an arbor and rotated at high speed. If excessive pressure or force, directed laterally or radially inward, is applied to the brush during use, individual wire strands can break and fly off the rotating brush, risking injury to a user. Additionally, after one wire strand in a knot breaks, the remaining wire strands have less mutual support and become more prone to breakage, such that after a few wire strands in a knot have broken, the knot, and hence the brush, may be more vulnerable to catastrophic failure. In other words, wire strand breakage can lead to premature failure of a brush, long before the wire strands have worn away at their working ends due to use.

Prior attempts to decrease the risk of wire strand breakage include encapsulating the entire annular working portion of the brush in a resin material or thermosetting polymer that binds the wires in place. This type of resin bonding has typically been performed with brushes made from a collection of individual wire strands but not brushes with knotted wire strands. The resin material, commonly a synthetic elastomer, wears away gradually to continually expose a short length of the wire strands. The elastomer prevents the wire strands from flexing excessively. While in some cases, a wire strand breaks because it has been worked out of the elastomer, in other cases, when a wire strand breaks, the elastomer holds it in place on the brush. However, a solid disk has disadvantages as compared with individual wire knots in that the lateral sides of the wire knots are not exposed for contact with a workpiece, and a large amount of resin material is required relative to the number of wires or wire knots to be encapsulated.

SUMMARY

An exemplary embodiment of a rotary brush described herein includes a hub having a central bore, a plurality of wire knots extending radially outward from the hub and spaced apart from each other around an outer circumference of the hub, a thermosetting polymer encapsulating each wire knot, and substantially polymer-free spaces located between each adjacent pair of wire knots.

Another exemplary embodiment of a rotary brush includes a hub having a central bore and an annular working portion extending radially outward from the hub. The annular working portion includes a plurality of wire knots each encapsulated in a thermosetting polymer alternating with a plurality of substantially polymer-free spaces.

An exemplary method of making a rotary brush having alternating polymer-encapsulated wire knots and substantially polymer-free spaces around its circumference includes mounting a plurality of wire knots to extend radially outward from a hub having a central bore, the wire knots being spaced apart from each other around a circumference of the hub, and exposing a portion of each of the wire knots to a liquid thermosetting polymer while slowly rotating the hub about the central bore, thereby allowing the polymer to wick into gaps between individual wire stands in each wire knot.

Another exemplary method of making a rotary brush having alternating polymer-encapsulated wire knots and substantially polymer-free spaces around its circumference includes mounting a plurality of wire knots to extend radially outward from a hub having a central bore, the wire knots being spaced apart from each other around a circumference of the hub, exposing a portion of each of the wire knots to a liquid thermosetting polymer while slowly rotating the hub about the central bore, thereby allowing the polymer to wick into gaps between individual wire stands in each wire knot, ceasing exposing the portion of each of the wire knots in the bath after each wire knot has been exposed to the polymer, continuing to slowly rotate the hub until the polymer is at least partially solidified and curing the polymer while continuing to slowly rotate the hub.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWING

The following detailed description can be read in connection with the accompanying drawings in which like numerals designate like elements and in which:

FIG. 1 is a side view of an exemplary knot brush with encapsulated knots.

FIG. 2 is an expanded, partially cut away side view of a portion of the knot brush of FIG. 1.

FIG. 3 is an end view of the portion of the knot brush of FIG. 2.

FIG. 4 is a flow chart depicting a method of making an exemplary knot brush with encapsulated knots.

DETAILED DESCRIPTION

FIGS. 1-3 illustrate an embodiment of a rotary wire knot brush 10. The brush 10 includes a substantially circular hub 20 surrounded by an annular working portion 30. The hub 20 provides a structure for mounting and retaining a plurality of radially extending wire knots 32, while the wire knots 32 form the working portion 30 of the brush.

Each wire knot 32 includes several individual wire strands 34 that are doubled over themselves within the hub 20 so that free ends 36 of the wire strands 34 form an outer circumference of the working portion 30 of the brush 10. The wire strands 34 of each wire knot 32 are twisted together with each other about a radially extending axis. Each wire knot 32 is spaced apart from adjacent wire knots 32 on either side by a space 38, so that the working portion 30 has a generally evenly spaced distribution of alternating wire knots 32 and spaces 38 around the periphery of the hub 20.

The hub 20 can retain the wire knots 32 in various ways. In one embodiment, the hub 20 includes a disk (not shown) having a plurality of through holes in a circular pattern near an outer circumference of the disk, each hole being adapted to receive a bundle of wire strands 34 that are looped through the hole and then twisted upon themselves to form a wire knot 32. Alternatively, other equivalent structures may be used for retaining bundles of wire strands 34 that can be twisted upon themselves.

In the illustrated embodiment, a core 26 connected to an inner peripheral portion of the disk defines a central bore 28 to enable the brush 10 to be mounted on an arbor. A side plates 24 is positioned on each side of the disk and the side plates 24 are compressed axially inwardly against the wire knots 32 to retain the wire knots 32 in a radially outward orientation with respect to the hub 20. The side plates 24 may be held in position by the core 26 of the hub 20.

Each wire knot 32 is encapsulated with a thermosetting polymer 40, preferably an epoxy formed by combining an epoxy resin with a hardener. Encapsulation of the wire knots 32 helps inhibit breakage of the wire strands 34, and also allows the wire knots 32 to wear away at the free ends 36 of the wire strands 34. This prolongs the life of the brush 10 by allowing the brush 10 to ultimately be taken out of service due to wear (i.e., the free ends 36 of the wire strands 34 simply wear down) rather than due to breakage or fatigue failure of the wire strands 34. The thermosetting polymer 40 can be made from a selection of resin materials, including but not limited to a synthetic elastomer. The thermosetting polymer 40 is typically applied in liquid form but subsequently dries and hardens.

After the wire knots 32 are formed by twisting the individual wire strands 34, interstitial gaps exist between many of the wire strands 34 along at least a portion of the exposed length of the wire knot 32 between the hub 20 and the free ends 36 of the wire strands 34. The thermosetting polymer 40 is infused into at least a portion of the interstitial gaps so as to bond the separate wire strands 34 together into a unitary wire knot 32, at least partially encapsulating the wire knot 32. However, the spaces 38 between adjacent wire knots 32 are substantially devoid of polymer 40, so that the working portion 30 of the brush 10 comprises a plurality of separate encapsulated wire knots 32 rather than a solid polymer disk.

As shown in FIG. 4, an exemplary method 100 of making the brush 10 includes: a step 110 of mounting the wire knots 32 to a hub 20, a step 120 of exposing the wire knots 32 to polymer 40 while rotating the hub 20, a step 130 of ceasing to expose the wire knots 32 to the polymer 30, a step 140 of continuing to rotate the hub 20 until the polymer 40 becomes partially firm, and a step 150 of curing the polymer 40 while rotating the hub 20.

In one method of making the brush, thermosetting polymer 40 is applied to the brush 10 after the wire knots 32 have been formed and the side plates 24 are secured on the hub 20. The central bore 28 of the hub 20 is used to mount the brush 10 on an arbor that is slowly rotated as the brush 10 is exposed to liquid thermosetting polymer. As the brush 10 is rotated, the wire knots 32 can be exposed to polymer by any of several methods, or by one or more of such methods simultaneously or in succession. Typically, the wire knots 32 are exposed to liquid polymer at about ambient temperature.

One method of exposing the wire knots 32 to polymer is by dipping an outer portion of each wire knot 32, in succession, into a bath of liquid polymer as the brush 10 is rotated. Each knot 32 can be dipped one or more times depending on the characteristics of the particular liquid polymer. Another method of exposing the wire knots 32 to polymer is by dripping liquid polymer onto the wire knots 32 as they rotate past a source of liquid polymer located above the brush 10. Yet another method of exposing the wire knots 32 to polymer is by spraying liquid polymer onto the wire knots 32. When exposing the wire knots 32 to liquid polymer, the speed of rotation can be varied depending on several factors, including but not limited to the length of the wire knots 32, the diameter of the brush 20, the type of thermosetting polymer, the temperature at which the thermosetting polymer is applied, and the viscosity of the polymer. The speed of rotation allows for capillary action to wick the polymer between the wire strands 34 without creating so much centrifugal force as to cause the epoxy to be expelled from the free ends 34 of the wire knots 32. The viscosity of the liquid polymer is controlled within a range so that it is sufficiently thick to cling to the individual wire strands 34 without dripping off but sufficiently thin to penetrate into the interstitial spaces between the wire strands 34.

Each wire knot 32 need not be completely exposed to the thermosetting polymer (e.g., the depth of exposure of the brush 10 to the polymer bath can be less than or equal to the radial distance from the outer periphery of the hub 20 to the free ends 36 of the wire strands 34, or the stream or drops dripped onto the brush 10 need not be large enough to contact the entire length of the wire knots 32) for each wire knot 32 to be sufficiently encapsulated in polymer. For example, when a wire knot 32 is exposed at least partially into the polymer bath in the dipping method, the wire knot 32 is oriented at least partly in a downward direction with respect to the hub 20, so that the outermost portion of the wire knot 32 is most exposed to the polymer. Similarly, when a wire knot 32 is exposed at least partially to the polymer by the dripping method, the wire knot 32 is oriented at least partially in an upward direction with respect to the hub 20, so that liquid polymer can wick down, both by gravity and capillary action, from the free ends 36 of the wire strands 34 toward the hub 20. The small size of the interstitial spaces between the individual wire strands 34 in the wire knot 32 enables the thermosetting polymer to be wicked upward or downward into portions of the wire knot 32 closer to the hub 20 that were not dipped into the polymer bath or directly contacted with dripping liquid polymer. However, because the wire knots 32 are sufficiently far apart and the exposure of the wire knots 32 to the polymer bath, drip, or other exposure mechanism is sufficiently brief, the polymer does not bridge the spaces 38 between the wire knots 32. As a result, the spaces 38 between each pair of adjacent wire knots 32 remain substantially free or devoid of polymer.

Gravity may be used to aid capillary action in filling the interstitial gaps, since as the brush 10 is rotated further, the wire knot 32 passes through a continuum of orientations at least partly in an upward direction with respect to the hub 20. Consequently, any polymer remaining in a liquid state will be urged by gravity to flow downward along the wire knot 32 toward the hub 20, filling the interstitial gaps between the wire strands 34.

After all of the wire knots 32 have been exposed at least once to the thermosetting polymer, exposure is terminated while the brush 10 continues to slowly rotate. The brush 10 continues to rotate until the polymer is at least partially solidified, becoming sufficiently firm that polymer can no longer drip off of the wire knots 32. The continued rotation prior to firming up of the polymer helps ensure that the distribution of polymer in each of the wire knots 32 is substantially similar and allows any excess polymer that is not wicked into the interstitial gaps between the wire strands 34 to drip off before drying.

After the wire knots 32 have been encapsulated and the polymer at least partially solidified, the hub 20 can be stopped from rotating, if necessary, for a period of time so that the brush 10 can be transferred to another arbor which will rotate the hub 20 while the polymer is cured. It is also possible to keep the hub 20 mounted on the same arbor, and to keep the hub 20 rotating, while the brush 10 is transferred for curing.

In one embodiment, the polymer is cured by heating in a curing oven. During curing, the brush 10 is heated so that the polymer reaches its glass transition temperature and becomes fully hardened. However, while the polymer is being heated and before it is fully cured, the polymer decreases in viscosity, which further enables the polymer to wick into the interstitial spaces between the wire strands 34. To enable uniform distribution of the polymer and to prevent polymer from dripping off as it heated, the brush 10 is rotated during curing, which has the benefit of allowing gravity to periodically assist capillary action in infusing the polymer into the interstitial spaces between the wire strands 34. In another embodiment, the polymer is cured by exposure to ultraviolet light.

Prior to exposing the wire knots 32 to the thermosetting liquid polymer, the liquid knots 32 may be exposed to an enhancement material in a step 115 of exposing the wire knots 32 to an enhancement material. In one example, the enhancement material can be a lubricant that coats the wire strands 34 prior to encapsulation in polymer. When the brush 10 is in use, the polymer 40 wears away exposing the lubricant-coated wire strands 34, such that the lubricant reduces the friction between the wire strands 34 and a workpiece, which results in less heating in the wire strands 34 and prolongs the life of the brush 10. In another example, the enhancement material can be a coolant. In yet another example, the enhancement material can be an encapsulant, such as a thermosetting polymer have a composition the same as, or different from, that of the polymer 40.

The resultant wire brush 10 has all of the advantages of a fully encapsulated brush at significantly less cost in thermosetting polymer. In addition, the wire brush 10 is lighter than a fully encapsulated brush and provides enhanced abrasion qualities by leaving the flanks of each wire knot 32 exposed and able to contact the workpiece. In addition, production of the wire brush 10 is simpler and faster than a fully encapsulated brush since no mold or other casing is needed to retain the polymer while it hardens.

The thermosetting polymer 40 may be clear, so that the individual wire strands 34 in the wire knots 32 are visible, or the thermosetting polymer 40 may have an added dye or colorant to provide an enhanced appearance.

Although described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without department from the spirit and scope of the invention as defined in the appended claims. 

1. A rotary brush comprising: a hub having a central bore; a plurality of wire knots extending radially outward from the hub and spaced apart from each other around an outer circumference of the hub; a thermosetting polymer encapsulating each wire knot; and substantially polymer-free spaces located between each adjacent pair of wire knots.
 2. The rotary brush of claim 1, wherein each wire knot comprises a plurality of wire strands twisted together about a radially-oriented axis;
 3. The rotary brush of claim 2, wherein each wire knot further comprises gaps between the wire strands, and wherein the polymer fills at least a portion of the gaps to help support the wire strands.
 4. The rotary brush of claim 1, wherein the thermosetting polymer includes an epoxy.
 5. The rotary brush of claim 4, wherein the epoxy includes a synthetic elastomer.
 6. A rotary brush comprising: a hub having a central bore; an annular working portion extending radially outward from the hub, the annular working portion including a plurality of wire knots each encapsulated in a thermosetting polymer alternating with a plurality of substantially polymer-free spaces.
 7. The rotary brush of claim 6, wherein the thermosetting polymer includes an epoxy.
 8. A method of making a rotary brush having alternating polymer-encapsulated wire knots and substantially polymer-free spaces around its circumference, the method comprising: mounting a plurality of wire knots to extend radially outward from a hub having a central bore, the wire knots being spaced apart from each other around a circumference of the hub; and exposing a portion of each of the wire knots to a liquid thermosetting polymer while slowly rotating the hub about the central bore, thereby allowing the polymer to wick into gaps between individual wire stands in each wire knot.
 9. The method of claim 8, wherein exposing a portion of each of the wire knots to a liquid thermosetting polymer includes dipping an outer portion of each of the wire knots in a bath of the polymer.
 10. The method of claim 8, wherein exposing a portion of each of the wire knots to a liquid thermosetting polymer includes dripping the polymer onto an outer portion of each of the wire knots.
 11. The method of claim 8, wherein exposing a portion of each of the wire knots to a liquid thermosetting polymer includes spraying the polymer onto an outer portion of each of the wire knots.
 12. The method of claim 8, further comprising: ceasing exposing the portion of each of the wire knots to the polymer after each wire knot has been exposed to the polymer.
 13. The method of claim 8, further comprising: continuing to slowly rotate the hub until the polymer is at least partially solidified.
 14. The method of claim 13, further comprising: curing the polymer while continuing to slowly rotate the hub.
 15. The method of claim 8, wherein the thermosetting polymer includes an epoxy.
 16. A method of making a rotary brush having alternating polymer-encapsulated wire knots and substantially polymer-free spaces around its circumference, the method comprising: mounting a plurality of wire knots to extend radially outward from a hub having a central bore, the wire knots being spaced apart from each other around a circumference of the hub; exposing a portion of each of the wire knots to a liquid thermosetting polymer while slowly rotating the hub about the central bore, thereby allowing the polymer to wick into gaps between individual wire stands in each wire knot; ceasing exposing the portion of each of the wire knots in the bath after each wire knot has been exposed to the polymer; continuing to slowly rotate the hub until the polymer is at least partially solidified; and curing the polymer while continuing to slowly rotate the hub.
 17. The method of claim 16, wherein exposing a portion of each of the wire knots to a liquid thermosetting polymer includes at least one of dipping an outer portion of each of the wire knots in a bath of the polymer, dripping the polymer onto an outer portion of each of the wire knots, and spraying the polymer onto an outer portion of each of the wire knots.
 18. The method of claim 16, further comprising: exposing a portion of each of the wire knots to an enhancement material prior to exposing a portion of each of the wire knots to the polymer.
 19. The method of claim 18, wherein the enhancement material is selected from the group consisting of a lubricant, a coolant, an encapsulant, and combinations thereof.
 20. The method of claim 16, wherein the thermosetting polymer includes an epoxy. 